Resistance coatings



July 2, 1957 w. M. KOHRING RESISTANCE COATINGS Filed April 6. 1953 IN VEN TOR.

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W MaKMdw/L ATTORNEX5- RESISTANCE COATINGS Wilbur M. Kohring, Lakewood,@hic Application April 6, 1953, Serial No. 347,114

6 Claims. (Cl. 20156) This invention relates to electronic circuits, andinvolves preparation of such by selective application of metal coatingon insulation supports of various desired form. By the presentimprovements, these devices can be made with particularly convenientlarge scale operation, and economical usage of metal and with savings ingeneral costs. Other objects and advantages will appear from thefollowing description.

To the accomplishment of the foregoing and related ends, said invention,then, comprises the features hereinafter fully described andparticularly pointed out in the claims, the following description andthe annexed drawing setting forth in detail certain illustrativeembodiments of the invention, these being indicative, however, of but afew of the various ways in which the principle of the invention may beemployed.

In said annexed drawing:

Fig. 1 is a perspective view showing an embodiment of the invention;

Fig. 2 is a fragmentary sectional view of modified detail of structure;

Fig. 3 is a fragmentary larger scale detail section of a furthermodification;

Fig. 4 is a perspective view of another embodiment of the invention;

Fig. 5 is a fragmentary enlarged section on the line V, Fig. 4;

Figs. 6-11 inclusive show stages in preparing resistances of cylindricalform;

Fig. 12 is a side elevational view illustrating such finished devices;

Figs. 13 and 14 are fragmentary elevational views showing modifiedterminals;

Fig. 15 is a fragmentary perspective, and Fig. 16 a fragmentary sectionshowing other modified terminals;

Figs. 17 and 18 are broken plan views illustrating printed circuitconstruction in accordance with the invention; and

Fig. 19 is an edge view thereof with the masking pattern plate inassembly.

In general, the invention involves selectively applying a thin metalsurfacing to a portion of the surface only of an insulation support, andproviding suitable terminals. In particular, the portions of theinsulation support which are not to be metalized are covered by masking,and then the metalizing is performed by vacuum deposition. Masking whichmay be used may be tape, wax, water glass compositions including finelydivided mineral filler, pattern plates of metal, synthetic resin, etc.The vacuum depositing is on the order of the known technique, the metalbeing vaporized by heated elements or filaments in a chamber under highvacuum, such as those commercially available as produced by DistillationProducts Company, and the generally well known technique, as forinstance Vacuum Technique by Saul Dushman (Pub. by John Wiley & Sons,Inc., N. Y., 1949), pp. 757-764. Metals which may be thus applied arePatented July 2, 1957 for instance nickel, iron, chromium, cobalt,iridium, platinum, silver, gold, aluminum, zinc, copper, alloys of twoor more such, commercial alloys such as Invar, Constantan, etc. Theinsulation support may be of ceramic material such as porcelain,steatite, glass, rubber, thermo-setting or thermo-plastic syntheticresin, fiuor compound resins, such as polytetrafluoroethylene,polychlorotrifiuoroethylene and the like (Tefion, Kel- F), as preferredin any particular instance. Metals of desired thermal coeflicient can beapplied individually, or simultaneously, and by selection relative alsoto resistance characteristic, the end result may be controlled to arange desired. Such metals as nickel, iron, chromium, etc., being ofhigh resistance character for instance, and such metals as copper andsilver being of low resistance character, and particularly useful inalloying combinations. Metals of low thermal coefficient are nickel,iron, chromium, platinum, iridium, tantalum, tungsten; while aluminum,manganese and zinc are in relatively high range of thermal coeflicient;and silver and copper in intermediate range.

The shape and character of the insulation body is contingent upon thefinal form of structure which is desired. Referring to Fig. 1, aninsulation body 2, as of ceramic, is of general disc form, open at thecenter and a sector of the periphery at one point. Such ceramic blank ismasked except for the particular limited surface which is to beresistance metalized, the masking for instance being a close-fittingsheet metal pattern plate with cut-out corresponding to the area toreceive the metal-coating, or it may be a pressure-applied adhesivetissue pattern with cut-out, or it may be a water glass composition or ahigh-melting wax applied on the insulation body except the area which isto receive the metalizing. Thus, in Fig. 1, such surface for metalizingmay be of the partial circular form 3 on the face of the insulation body2. The insulation body thus masked except for the limited surface to bemetalized, is then subjected to vacuum deposition of for instance anickel-iron alloy containing about 36 percent nickel. The metal depositson the exposed area, in this instance the incomplete-circular strip 3.This may be of uniform width throughout its extent, or in some cases itis preferred to have it in tapered form, wider at one extremity than theother. The metal adheres tightly to the insulation body, and the maskingis removed, and terminals 4, 8 are applied, one connecting to the end ofthe metalized area, and the other to a central movable contactor 6 whichis secured to the rotatable shaft 7 in form as known. Or a terminal 5may give a potentiometer connection.

In some instances instead of applying the metal to a limited surface ofthe entire support, a separate resistance insert may be prepared, and asillustrated in Fig. 2 this may involve an insulation body 2' which maybe of general near-circular form corresponding to the path of contactdesired in a structure of the type of Fig. l, and such body, maskedexcept for its one exposed working surface is then subjected to thevacuum deposition and metal coat 3 is applied. Then on removing themasking, the body 2' is mounted with synthetic resin base B and isfinished with terminals and contactors as in the form of Fig. 1. In somecases instead of the crosssectional form of insulation body 2' as inFig. 2, a desirable form is that of 2", Fig. 3, in which, consideringthe structure to be of overall near-circular type, inner and outergrooves 10 facilitate application of masking other than. liquid wax, forinstance adhesive tape or a contractile rubber.

In similar procedure, a rheostat or potentiometer, depending upon whichterminals are connected up, may be made in a form as illustrated inFigs. 4 and 5. Here, the

insulation body 2a is a cylinder such as of ceramic, steatite, glasscomposition, synthetic resin, fluor compound resins, etc., with a shaft7a for rotation, and is mounted in a support or frame 10 such as ofsynthetic resin insulation. The periphery of the cylinder carries ahelical strip or pathway of vapor-deposited metal of resistancecharacter, and moving contact is made with such pathway of resistance byslidercontacts 6a. Thereby the amount of the resistance path, andconsequently the amount of resistance can be varied as desired, byappropriate rotation of the cylindrical body. While the resistance pathmay be a plain helical strip of the deposited metal on the periphery ofthe insulation cylinder, and the slider-contacts travel on a threadedrod having the same pitch as that of the resistance helix, and with agear on the outer end of the rod and a coacting gear on the shaft 712,it is preferable to form the resistance path as a groove. Thus, thecylindrical body is grooved as at 3a, and in the groove is the coatingof deposited resistance metal. The sliders coact with this by ridingfreely on a fixed rectangular-section bar 11 mounted in the frame 10.Thereby, as readily seen, the sliders 6a, which as seen by the enlargeddetail at Fig. 5 have a spring finger which terminates in a rounded end12 fitting the groove. When the cylinder is turned in either direction,the easy-riding slider travels the groove and has its position adjustedthereby. From the sliders 6a flexible conductor cords 13 lead toterminal screws 14 to which outside connections may be made. Anotherterminal 15 with a spring finger 16 makes completion of the desiredcircuit by riding resiliently on the metal-coated end 17 of thecylinder. The metal is deposited on the selectively desired areas of thecylinder after first applying masking to cover the portions where themetal is not desired, such as the periphery between grooving, and theinactive end of the cylinder. Masking which may be employed for this maybe applied as a water glass and filler composition, or a high-meltingwax, or the masking may be a pattern templet withappropriate cut-outthrough which the metal is to deposit on the cylinder, and such templetmay be formed of suitably distortionless sheet regenerated cellulose orplastic, and it is further advantageous to coat the inside surface withadhesive which adheres by application of pressure, and the templet afteruse can be stripped off. The vacuum depositing of the metal is asafore-described. This device by making outside circuit connections tothe terminal 15 and one of the terminals 14 functions as a rheostat, orby using the terminal 15 and both terminals 14 it functions as apotentiometer.

Where a resistance of rod-like form is desired, a solid rod ofinsulation, 25, Fig. 6 may be subjected to the vacuum-depositionmetalizing to make a coat 3b. The end surfaces may be masked or not, asdesired. Depending upon the length of the insulation rod, it may aftermetalizing, be severed, as indicated at the dotted line 12, to formseparate units, or it may be employed as a whole without severing, toform one unit. To facilitate and simplify severing of metalized rodsinto multiple unit products, I prefer to start with rods which arecircumferentially scored as at 13, Fig. 7, and such scoring may be atdistances desired for respective lengths. This form of rod after beingmetalized is easily snapped into its segments without requirement ofspecial severing means. While the forms just noticed are solid bodies,hollow units are preferable in some instances, and as shown at Fig. 8, atube of insulation 20 may have its ends masked, and be subjected tovacuum deposition, thereby metalizing the exterior surface of the tubeas coat 3c. Again, such metalized tube may be employed as a whole as aunit, or it may be severed into a plurality of units. Again, severing insuch case is preferably facilitated by circumferential scoring 13, Fig.9. Where an especially protected construction is preferred, theinsulation tube may be masked on the outside, and then subjected tovacuum deposition metalizing, thereby depositing the metal 3d on theinterior surface or bore of the tube, as illustrated in Fig. 10. Again,this may be finished up as a whole unit, or it may be severed to aplurality of smaller ones. And, again, the provision of circumferentialscoring 13, Fig. 11, greatly facilitates and simplifies the sub-dividingof thetube into desired unit lengths. The units thus produced areequipped with end terminals, and as shown in Fig. 12 these may be metalcaps 20 with riveted-on terminal wires 21, the caps being engaged overthe ends and contacting the peripheral metal resistance coating.Preferably, these caps are provided with a small cut-out 22, in whichapplication of solder may assure both retention and complete adequacy ofcontact. Instead of a cut-out 22 as foregoing, the caps may have simplya cut 22a, Fig. 13, this affording a more resilient grip on the end ofthe cylindrical body and its peripheral resistance coating, and again asmall amount of solder may be applied in the cut to make sure ofretention and completeness of contact. As shown in Fig. 14, the terminal2012 may be in the form of a short helix which engages over the end andexerts resilient holding, and a small amount of solder may be alsoapplied. Instead of a helix-form terminal, a flat spiral, 20c may beemployed, as in Fig. 15, and here the end of the insulation body mayhave been metal coated in the vapor deposition, or it may receive acoating of colloidal silver or the like, and soldering may complete theunion. Or, as in Fig. 16, the terminal 20d may be of a form to insertinto an end opening or bore in the insulation body, and again the lattermay have deposited metal on the end or it may receive an application ofcolloidal silver, and be cemented or soldered into secure union.

In some simple cases, the shape of the insulation body is such as torender it more easily to apply the vacuum deposited metal over thesurface, and then grind off portions where it is not to function.Thereby time may be saved over the operations of masking and thenfinally removing the masking. Ordinarily, however, where a patterntemplet can be applied, this is particularly satisfactory.

By the present invention, circuit parts, or an entire circuit may beprovided, as desired in any case, by the vacuum depositing of the metal.In Fig. 18 there is illustrated thus printed electronic circuit means inaccordance with the present invention. On a plate of insulation 2e, ofmaterial as preferred, ceramic, synthetic resin insulation, or other, amasking pattern templet is applied in close contact with the surface ofan insulation plate, this pattern templet having cut-outs in accordancewith the form of the circuit elements to be deposited on the insulationplate. Thus, illustratively, there may be a resistance 3e in the form ofa sinuous path of deposited metal between points 24, 25, or forparticularly low resistance the deposited metal may be in the form ofparallel lines 3e, as between points 24 and 26. Such latter may haveopenings to receive mounting prongs from transistors, small tubes, orother elements at the back of the plate. As required by the exigenciesof any particular circuit, there may also be interposed as betweenpoints 26 and 27 units 28 with their terminals connecting at 26 and 27respectively, such units being conventional capacitors, resistors, etc.,and their wire terminals may be passed through the openings at 26, 27and be soldered in circuit. Again by the present method a resistancebetween points 25 and 30 may be laid down in zig-zag form 32'', or theresistance may be of varied form as indicated in the showing. Also,printed circuit elements such as capacitors may be formed on theinsulation plate, as a plurality of spaced-apart line deposits 31,connecting between points 32 and 33. In such manner, as readily seen,printed circuit combinations of capacitance and resistance may beapplied all at once for a complete circuit outfit with such elements asrequired in any particular case, and. the other elements such astransistors or small tubes may be assembled by the mounting holes. Themasking is particularly conveniently accomplished by a pattern templetwith cut-outs appropriate to the particular detail circuit which is tobe printed. And, a templet thus may be a thin sheet 35 of resilientmetal, steel, brass, etc. And by providing this with a rebent flange 36,the templet may be easily and quickly clamped onto the plate and be heldby such flange in resiliency, in adequate close contact with theinsulation body plate 22. Another satisfactory masking templet is ofsuitable distortionless sheet organic material, regenerated cellulose,synthetic resin plastic and the like, with the cut-outs appropriate forthe particular circuit to be printed, and such sheet by application ofan adhesive coating sensitive to pressure, may be adhered to theinsulation body plate which is to be printed, and after subjecting tothe vacuum deposition operation, the templet may be easily stripped off.

Where merely connecting line paths between points are wanted incompleting any desired circuit, as illustrated at lines 23, Fig. 17, theappropriate pattern templet therefor is applied to the insulation plate,and the metal vapor-deposited is of particularly conductive order, suchas silver, copper, etc., or alloys. The technique being as described.

As an example: A ceramic blank of flat cut-circular form is providedwith masking except for a resistance path desired on the fact. Themasked blank is inserted in a chamber equipped With connections for highvacuum, and with filament heating means and feed-metal of about 36percent nickel, the remainder iron. With air pressure reduced to a smallfraction of an inch, and vaporization of the nickel alloy, the vaporsdeposit, condensing on the blank. And on removal from the chamber, andclearing off the masking, and applying terminals, soldering as necessaryto the deposited metal strip for circuit-completion, the device is thusquickly and simply manufactured. Depending upon which terminals are putinto the outside circuit, the device functions as a rheostat or as apotentiometer.

As another example: A cylindrical ceramic blank with helical grooving ismasked between grooves, and also on the inactive end, and is placed inthe vacuum chamber and subjected to metal vaporization and deposition asforegoing. And on removal, and clearing off the masking, the cylinder ismounted in an insulation framing equipped with slider-contacts to ridein the grooves as they freely slide along on a guide bar and an endcontact. Depending upon the particular outside connections made, thedevice functions as a rheostat, or as a potentiometer.

As another example: Cylindrical blanks, with spaced circumferentialscorings are placed in the vacuum chamber and subjected to vapordeposition of metal as foregoing. On removal, these cylindrical blanksare snapped into unit pieces, and are equipped with terminals at theirends, for unit resistors.

As another example: An insulation plate of ceramic having holes spacedin accordance with the particular circuiting which is to be provided, isassembled with a masking pattern templet which has cut-outs for allowingvaporized metal to deposit on the insulation surface at the pointsrequired and in form as desired. A masking is applied to the back andedges of the plate, to prevent metal deposit there. And this assembly isput into the vacuum chamber and the metal is vaporized and deposited asforegoing. On removal, the pattern templet is taken off and othermasking is removed, and the metal is found deposited in the preciselines determined by the templet. Transistors, tubes and other pro-formedaccessories as required by the particular circuit which is in view, arethen assembled with the plate.

As another example: An insulation plate having holes spaced inaccordance with a particular circuiting which is desired, is assembledwith a pattern templet which has cut-outs for allowing vaporized metalto deposit in generally line-form on the insulation surface to make outconducting paths. Masking is applied to the back and edges of the plateto prevent metal deposit there. This assembly is put into the vacuumchamber and silver is vaporized and deposited as foregoing. On removal,the pattern templet is taken off and other masking is removed, and thesilver lines are found printed for the circuiting on the face of theinsulation plate. Then, this surface is covered with masking, andlikewise the edges of the plate, and a pattern templet with cut-outs forcircuit elements, resistances, capacitance, etc., as desired, is appliedto the other face of the plate. And the assembly is put into the vacuumchamber and a metal having resistivity of the extent desired for theparticular work in view, for instance a nickel alloy, is vaporized anddeposited through the pattern templet. On removal, the templet is takenoff, and also the masking. The plate presents conductive circuitinglines printed on one face and circuit elements, resistances, etc.,printed on the other. Transistors or tubes and completing connections asrequired are added to finish the desired assembly.

Resistance surfaces thus prepared are unique in that the deposited metalis characteristic and recognizable, and has a uniformity, and a finenesswhich is sui generis, and having an exceptionally fine finish andsmoothness of surface, which is notably advantageous for slidingcontactors. It is particularly noticed that this is in contrast to anymetal deposit formed by electro-plating or by heating of colloidal metalcompositions, as such electro-deposited or decomposed colloidalcompositions have over-formed crystalline texture. And, the present kindof metal deposit is also very different in nature from deposited orflashed carbon which is of crystalline and abrasive character. The metalmolecules in changing state from vapor to solid at the interface of thenon-metallic body attach thereto with particular tenacity anddurability. The thickness of deposit can be as desired, from a fewhundred thousandths of an inch to several times that thickness. A smallamount of supply metal provides an adequate dense tough coat on a verylarge number of blanks.

Other modes of applying the principle of the invention may be employed,change being made as regards the details described, provided thefeatures stated in any of the following claims or the equivalent of suchbe employed.

I therefore particularly point out and distinctly claim as my invention:

1. In a device of the character described, a cylindrical insulationbody, a helical groove on its periphery, vacuumdeposited metal coatingin the groove, a shaft for rotating the cylindrical body, a firstcontactor in electrical contact with said metal coating, a secondcontactor traveling in the groove relative to said first contactor, andan insulation bar on which said contactor freely slides.

2. In a device of the character described, a cylindrical insulationbody, a helical path of vacuum-deposited metal coating on its periphery,a shaft for rotating said body, a first contactor in electrical contactwith such metal path, and a second contactor mounted for movement on themetal path relative to said first contactor upon rotation of the body,thereby to vary the length of that portion of the path between the twocontactors.

3. In making a device of the character described, pro viding acylindrical insulation body with a helical groove, masking the surfacesexcept for the groove, depositing a resistance metal coat in the helicalgroove, and removing the masking.

4. In making a device of the character described, masking a cylindricalinsulation body except for a helical path, vapor-depositing a resistancemetal at the exposed helical path, removing the masking, and mounting acontactor for relative movement on said path.

5. In making a device of the character described, masking a cylindricalinsulation body except for a helical path on its periphery and one endthereof from which such path extends, vapor-depositing resistance metalat the ex posed helical path and end, removing the masking, mounting acontactor for relative movement on said path, and

mounting a second contactor in engagement with such end. a

6. In a device of the character described, a cylindrical insulationbody, a helical path of vacuum-deposited metal coating on its periphery,a similar coating of metal on one end of the body connected electricallyto such metal path, a shaft for rotating said body, a first contactortraveling on the metal path, and a second contactor engaged with themetal-coated end of the body.

References Cited in the file of this patent UNITED STATES PATENTS1,303,404 Simon May 13, 1919 1,676,869 Richter July 10, 1928 1,859,344Ruben May 24, 1932 2,118,072 Deutschmann May 24, 1938 8 Potter Aug. 7,1945 Hood Apr. 8, 1947 Eisler May 25, 1948 Palya June 1, 1948 HowellMar. 21, 1950 Jack et a1 Jan. 9, 1951 Sullivan Feb. 20, 1951 HathawayJune 10, 1952 Luhn Nov. 4, 1952 Schleuning Sept. 7, 1954 OTHERREFERENCES Printed Circuits, Dept. of Commerce, Nat. Bur. of Stds. Circ.468, Nov. 15, 1947, especially pages 2427. 15 Publication 192, NewAdvances in Printed Circuits,

Nat. Bureau of Stds., Nov. 22, 1948.

